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Also think the aux is a good idea and have one similar to KevinAZ's choice mounted in front of radiator.

According to a couple of AC websites, the average drop across a good downflow radiator is 20-35 degrees depending on ambient temp and if car has AC running or not. Assuming no AC, good flow in radiator, a 160 degree thermostat and 80 degree day, then min water temp out should be in neighborhood of 125-140. Obviously best case scenario. At any rate, if those numbers correct whether cooler is in radiator or external path, trans fluid will never be below 125 assuming best case.

Have no idea of how hot trans fluid gets--probably in 200+ range-- and how much flow there is but would assume it moves fairly quickly across the cooler. Probably not much time for transfer. As I recall, the cooler is essentially 2 or 3 flat chambers spaced about 1/4 apart with fluid going in what appears to be in parallel and water surrounding. Fairly large surface area but again, unknown flow rate.

With an aux cooler after the water cooler, then water could remove part and air part so should be fairly cool yet still warm enough when going back to trans. Anyway, even the water cooler beats none at all which was the way a lot of 50's cars came.

EDIT: Haven't heard of that many failing due to leaks between fluid and water but more because the radiator inlet and outlet connections rust away to nothing and spring a leak.

Randy old friend, I enjoyed your dissertation but what you fail to realize is that, logic, common sense, and facts are, to some, not relevant when forming a position.

Also, what seems missing in this discussion is appreciation for the fact that hydraulically actuated apparatus like a transmission are regulated by pressure which is a function of viscosity, which is a function of temperature. Now no one wants an overheated transmission, but the Packard factory unit was (presumeably) designed to keep the fluid within a certain temperature range which provided the viscosity which then established spring pressures, orifices, etc. So you could speculate that a radiator-mounted cooler, driving across Dave Kenney's country in February into a freezing wind, would result in viscosities and hence pressures outside of the engineering design parameters. Also I wonder how well a radiator-mounted cooler does crawling along in a July 4th parade on a 110 degree day when there is little to no air flow across it? I'm beginning to think that, if you must have an radiator-mounted air cooler, perhaps having it in series with the original as you have done may be the best answer.

Randy And O-D, Those are both very good postings. The way I understand the purpose of the OE fluid to fluid heat transfer coolers is that they are intended to keep the transmission oil in an ideal temperature range and not simply to cool the oil otherwise cars would have been designed that way. It is possible and even likely that an auxiliary cooler will overcool transmission oil if the ambient temperature is low. The tranmission shop technicians I deal with recommend that an auxiliary cooler be covered or disconnected in winter to allow the transmission oil to warm up along with the engine. As has already been noted the ideal method to install an auxiliary cooler if one is needed is to place it in series with the rad cooler/warmer.

Thanks Dave, Randy and I both appreciate your comment and thoughts. Another issue to think about along the lines you mention is that excessively cooled fluid will resist flow more which could have a detrmental affect on lubrication efficiency, so in the end it's all a balancing act. I think you hit it right on the head, the OE can maintain a range, heating when (and if?) necessary, which an air cooler cannot. How relevant that is has yet to be determined, at least to me.

I have a thermocouple which I'm thinking about feeding thru the fresh air vent and down the trans dip stick tube into the pan, and setting up a recorder on the front seat to get some actual data. I'm running just a radiator-mounted cooler on the basis of a recommendation of my TU rebuilder, but there are many other 56s running around the neighborhood with the original cooler so that it should be easy to get some hard comparative data, though it will take some time to collect the data from both cars under similar operating conditions.

Dave, You are welcome. I am sure we would all be very interested in the results of your study. Would one of those laser thermometers be of assistance by simply measuring temperatures on the bottom of the trans oil pan and comparing the readings to a OE equipped Packard without the auxiliary cooler? I have one and it is quite accurate and you might get your readings without jacking up the car.

Brian,

To answer your question about the transcooler construction, the two halves are stamped steel, and appear to be crimped, and then sweated together. Internally the cooler has a metal hardline tubbing that is coiled in a elongated oval to give as much transfer surface as possible. In '54 in there were at least 2 versions of this cooler. One for the normal passengers cars, and then a "Heavy" duty version which I imagine was for the Commercial Chassis. The difference is the diameter of the tubing and larger trans line fittings.

When I replaced mine with a NOS unit, I also replace all the trans lines. But I put in a small 5 inch long spliced-in section in one line towards the front. So in the future I could easily remove the spliced section and attach a aux cooler in line without have to cut into the hard line.

As stated by others, the OEM cooler tended to rust at the water hose connections. Sweating brass ends on would be an improvement. On the NOS unit I acquired, I repainted it in the Eastwood Chassis black, and also painted the inside of the hose connectors to hopefully ward off rust a little longer.

Also I agree the fluid transfer design is not unique. Almost every car produced in the last 40 years with an automatic transmission has had the transcooler in the bottom of the radiator. I haven't seen anything in the news recently about a massive recalls do to chronic coolant/trans fluid leakage.

I think if a part starts to fail after 50 years, then it was a pretty well designed part. I cant think of many things on a new car that would last 50 years without replacement.

Just my $.02

I have a bourdon tube type water temp gauge. Anyone see any reason why i couldn't just drop the end of the bourdon tube down the 56 dip stick tube to get some readings????

I usualy don't like electric gauges. But maybe the electric gauge sending unit could be adapted to the T'Ultra drain plug????

I installed a VDO oil temperature gauge on the oil pan of my 83 Volvo. I drilled and tapped the oil drain plug for the sender unit and it works fine. I imagine that a similar gauge would work on an auto trans such as a T/U.

Wouldn't you want to measure the trans fluid temp before it gets to the cooler and the not the colder pan temp? They don't measure engine temp at the bottom of the radiator for example.